The present invention relates a method for dry cleaning the interior of a semiconductor manufacturing apparatus for use in performing microfabrication or film formation on substrates during the manufacturing processes of semiconductor devices. In addition, the invention also relates to a method for manufacturing semiconductor devices by use of a semiconductor manufacturing apparatus having its inside cleaned.
In processes for the manufacture of semiconductor devices, the attachment or adhesion of dust (contaminants) to substrates under manufacture causes pattern defects in the target devices, which in turn reduces the production yield during the manufacturing processes.
In currently available manufacturing processes, some processes are becoming more important, including dry etching technology using plasma, chemical vapor deposition (CVD) and the like. More specifically, such processes are designed to perform microfabrication, such as film formation, etching and the like, by utilizing plasma reaction of various kinds of gases introduced into the apparatus. During execution of these processes, deposition films tend to be left on and to adhere to the inner walls of the manufacturing apparatus being used, as the target substrate is being subjected to such microfabrication. One example is in dry etching, wherein certain deposition films adhere to the inner walls of the apparatus due to decomposition or combination of etching gases within a plasma and also due to generation of secondary etching products during etching. As wafers to be processed increase in number causing the film thickness to increase accordingly, such deposition films badly behave in that they partly peel off and then act as dust or contaminants which cause pattern defects in the devices being manufactured. Accordingly, it is necessary for such adhesion deposits to be removed periodically.
Conventionally, one typical approach to removal of such adhesion deposits is the so-called wet cleaning technology--i.e. wiping out the equipment by using a catalytic substance, such as alcohol or pure water or the like, while allowing the apparatus to be exposed to the atmosphere. Another prior known approach is a dry cleaning scheme using a combination of chlorine-based gas and fluorine-based gas, as disclosed, for example, in Published Unexamined Japanese Patent Application (PUJPA) No. 3-62520. A further approach is a dry cleaning technique using a plasma formed of a mixture of oxygen gas, and chlorine gas as disclosed for example in PUJPA No. 7-508313.
Unfortunately, the above-mentioned approaches have encountered serious problems as now will be discussed
First, with regard to the wet cleaning approach, it has been required that the apparatus be disassembled every time it is exposed to the atmosphere at constant time intervals; in addition thereto, the vacuum evacuation procedure is required after completion of every wet cleaning process. Obviously, this would result in termination of the operation of the apparatus for an increased time duration every time the cleaning treatment is done, which in turn leads to a noticeable decrease in working efficiency of the apparatus while reducing the throughput thereof.
Second, regarding the approach disclosed in PUJPA No. 3-62520, the material to be etched is an alloy containing therein Al and W, and therefore the technique disclosed therein is featured in that the cleaning steps for a plurality of etching objects are combined together in order to remove away Al's etching products as well as W's etching products. The third approach employing the dry cleaning technique as taught by PUJPA No. 7-508313 is featured by removing what is called the reaction products which originated from chemical reaction between the to-be-etched material and an etching gas being used or between a photoresist (carbon) employed as a mask layer material for etching and the etching gas or still alternatively due to polymeric bodies of the etching gas.
These approaches are completely silent about the cleaning of either ion sputtered matter or the "residue" of the materials of internal members of the apparatus or chemical compounds of the apparatus internal member materials and the etching gas being used, although these documents involve teachings as to how to clean up certain products resulting from chemical reaction between the etching gas and those materials left on wafer substrates, such as to-be-etched materials, mask materials and the like.
In the etching apparatus, a plasma created by the etching gas attempts to etch the substrate surface and simultaneously sputter the apparatus internal member materials also, which might result in attachment and adhesion of certain materials onto the inner walls of the apparatus, which materials may include, in addition to etching reaction products, either ion-sputtered matter of such apparatus internal member materials or chemical compounds of the apparatus internal member materials and of the etching gas being employed.
In other words, the dry cleaning methodology proposed to date is faced with a serious problem left unsolved: it is not possible to fully remove the ion sputtered matter or products of the apparatus internal member materials or the chemical compounds of such apparatus materials and the etching gas, which results in generation of contaminants due to delamination of resultant non-removed materials left on the inner walls of the apparatus.